The present invention relates to an electronic control system for glass gob distribution apparatus, and in particular to a system for controlling an electronic servo motor which in turn acts as the actuator for the glass gob distribution apparatus. Such apparatus is intended for use in glassware production machines comprising a plurality of individually controllable sections. Each section includes a molding assembly of single or multiple cavity design, and all of the various machine sections of the single machine are to be sequentially supplied with molten glass gobs. The gob distributor includes a set of arcuate scoops which receive a glass gob from the feeder assembly and which must be moved in proper sequence to direct the gobs of molten glass to the appropriate machine sections. Chutes are generally provided to direct the glass gobs to the several machine sections. In gob distribution apparatus for a multiple-gob forming machine, the apparatus includes a group of scoops matching in number the number of mold assemblies per section, and further includes a drive assembly for manipulating the scoop group so as to sequentially distribute the groups of glass gobs into a plurality of fixed chutes associated with preselected machine sections.
Various types of drives have been designed for gob distribution apparatus of the type described above. In the system of U.S. Pat. No. Re. 28,759, commonly owned with the present patent application, a scoop group has associated annular spur gears which are driven in unison via reciprocating rack gear through a predetermined schedule of angular displacements. A cam follower connected to the rack gear causes programmed movement thereof in response to rotation of a cam having lobes of suitable height to produce such predetermined schedule of angular displacements. Another approach, exemplified by U.S. Pat. No. 3,775,083, also commonly owned with the present application, uses air-driven actuators to produce programmed movement of rack gears in a system such as that of U.S. Pat. No. Re. 28,759. By properly setting up the exhaust ports in a plurality of pistons in such pneumatic actuators, the user establishes a predetermined schedule of angular displacement of the scoops.
In recent years, the patent art has included a number of gob distribution systems making use of an electrically actuated motor as a drive source for the gob distribution apparatus. One such system is disclosed in commonly owned U S. Pat. No. 4,599,101, the disclosure of which is incorporated herein by reference. This system uses a servomotor, advantageously a reversible DC motor, which is linked to a rack by a rotary-to-linear drive. The rack in turn mates with annular spur gears associated with the scoops in the manner of U.S. Pat. No. Re. 28,759, discussed above. This drive arrangement enjoys a number of advantages, including reduced backlash and the ability to more accurately place the scoop in a short period of time. To take proper advantage of the capabilities of this system, there is a need for an electronic drive system for the servo motor which will efficiently move the scoops subject to other constraints imposed by, e.g., the delivery of glass gobs by the feeder assembly, physical behavior of glass gobs during handling by the gob distributor assembly, etc.
A further problem area is the set up of the gob distributor assembly, and in particular the relative position and orientation of the gob distributor scoops and the chutes associated with the various machine sections. In prior art systems such as that of Pat. No. Re. 28,759, the placement of the scoops was severely constrained by the design of a particular cam, and hence to provide a proper alignment between the scoops in their delivery position of a given section and the chutes of that section it was necessary to adjust the latter. This limited form of adjustment was time-consuming and sometimes resulted in misalignments, which would lead to slaloming of the gobs during delivery, and other problems.
Accordingly, it is a primary object of the invention to provide an electronic drive system for achieving improved control over the motion of the scoops in a gob distributor.
Another object of the invention is to facilitate set up of the gob distributor. In particular, it is desirable to shorten the time acquired to align the gob distributor scoop with the troughs or chutes. It is furthermore desirable to reduce the extent to which the drive system interferes with this alignment process.
Yet another object is to enable the operator to adjust the alignment of the scoops and the troughs "on the fly", to reduce misalignments arising in actual operation.